Separable Microneedle Patch For The Treatment Of Bacteria-infected Chronic Wounds

Bacterial infection and tissue hypoxia are the two main obstacles that hinder the healing process of chronic wound.Antibiotics and hyperbaric oxygen therapy is often used as adjunctive modalities to treat them.However,these treatments are prone to problems such as bacterial resistance and oxygen toxicity.Sonodynamic therapy(SDT),which can produce abundant reactive oxygen species(ROS)under ultrasound exposure,can eliminate bacteria by disrupting their cell membranes.Its noninvasive property,high therapeutic efficacy and deep tissue penetration make SDT a promising therapeutic modality for combating various multidrug-resistant bacterial infections.Photosynthetic oxygen production with spatiotemporal controllability and excellent biocompatibility is an effective method to overcome tissue hypoxia.Microneedle is a novel transdermal drug delivery method,which has the advantages of painless minimally invasive,convenient use and low risk of accidental acupuncture.Microneedles are a transdermal drug delivery system that is painless,less invasive,and easy to self-administer,with a high drug bioavailability.Inspired by these,this thesis developed a separable microneedle patch to treat chronic wounds by simultaneously overcoming bacterial infection and tissue hypoxia.Firstly,CCM@ZIF-8 nanoparticles were prepared by encapsulating curcumin(CCM)into zeolitic imidazolate framework-8(ZIF-8)nanoparticles,followed by characterizing using dynamic light scattering(DLS),transmission electron microscope(TEM)and scanning electron microscopy(SEM).CCM@ZIF-8nanoparticles showed rhombic dodecahedral shape and a hydrated diameter of 233 nm.Then the composition was characterized by ultraviolet visible(UV-Vis)spectroscopy and fourier transform infrared(FTIR)spectrum,and the results demonstrated the successful encapsulation of CCM.Finally,the capacity for ROS generation under ultrasound conditions was tested using 2,7-dichlorofluorescein diacetate(DCFH-DA)and electron spin resonance(ESR).The results demonstrated that both singlet oxygen and hydroxyl radical were generated.Next,a detachable microneedle patch composed of soluble arrowheads and undissolvable support bases was prepared.The arrowheads were made of dissolvable poly(vinyl alcohol)/polyvinyl pyrrolidone(PVA/PVP)containing CCM@ZIF-8nanoparticles and the support bases were prepared using calcium alginate hydrogel encapsulating cyanobacteria.By testing the oxygen-producting capacity and stability of the support bases,it was found that the photosynthetic oxygen production performance of the hydrogel hardly changed after storage for 14 days.The puncturing ability and solubleness property of arrowheads on pig skin were tested.And it was demonstrated that the microneedles could successfully puncture the epidermal layer and the arrowheads could completely dissolve and release the encapsulated CCM@ZIF-8 nanoparticles within 120 seconds.Then,the in vitro bactericidal effect and cellular regulatory behavior of the microneedles were investigated.The results of the plate counting and live/dead fluorescence staining experiments showed that the microneedles achieved 100%killing efficiency to both Gram-positive pathogen Methicillin-Resistant Staphylococcus aureus(MRSA)and Gram-negative pathogen Escherichia coli(E.coli).The results of Alamar-Blue method showed that the microneedles had good cytocompatibility.And the oxygen produced by microneedles could effectively promote cell migration and regeneration,which could be reflected from the results of the scratch and Transwell assays.the results of the tubulogenesis assay demonstrated that microneedles Moreover,the results of the tubule generation assay demonstrated that the microneedles could efficiently promote HUVEC cells to form blood vessels.Finally,the therapeutic effect of the microneedles on bacteria-infected cutaneous chronic wounds was evaluated.Firstly,a mouse model of bacteria-infected cutaneous chronic wounds was established.treated and real-time recorded.The wound healing path was simulated by Image J software and the healing rate was calculated.The results showed that the microneedles can effectively accelerate the healing of chronic wounds.The results of hematoxylin and eosin(H&E)and Masson’s staining showed that the microneedles could facilitate epithelial regeneration and collagen deposition.The immunofluorescence analysis of CD-31 and HIF-α showed that there was no hypoxia and maximum neovascularization in the microneedle-treated mice.Moreover,the immunohistochemical analysis of TNF-α,VEGF and α-SMA showed that the microneedles could accelerate wound healing by effectively reducing the inflammatory response and promoting angiogenesis in the wound tissue.